1. Field of the Invention
The present invention relates to a valve timing control apparatus, which controls opening and closing timing of a valve that is driven by a camshaft through transmission of a torque from a crankshaft of an internal combustion engine.
2. Description of Related Art
In a known valve timing control apparatus, a first rotator and a second rotator are rotatable synchronously with a crankshaft and a camshaft, respectively. A planetary gear is meshed with a gear portion of the first rotator and a gear portion of the second rotator. A relative phase (hereinafter, referred to as an engine phase) between the crankshaft and the camshaft is changed through a planetary motion of the planetary gear.
Japanese Unexamined Patent Publication No. 2008-95550A (corresponding to US 2008/0083384A1) recites a valve timing control apparatus, in which stopper portions are formed in the second rotator that is coaxially received in the first rotator. When the stopper portions contact corresponding walls, respectively, of the first rotator in the rotational direction, the engine phase is limited. Here, when the engine phase is limited, the valve timing can be adjusted within an appropriate range, which is appropriate for driving the internal combustion engine.
In the case of the valve timing control apparatus recited in Japanese Unexamined Patent Publication No. 2008-95550A, the second rotator, which is supported by the first rotator, is constructed such that the stopper portions radially outwardly project at one axial end part of the second rotator to form a large diameter portion, and a small diameter portion is radially inwardly recessed from the large diameter portion at the other axial end part of the second rotator. Here, the axis of the second rotator can be easily tilted relative to the first rotator by vibrations transmitted from the internal combustion engine. As shown in FIGS. 8A-8C, the amount of tilt of the second rotator 1020 relative to the first rotator 1010 is determined as follows. That is, the second rotator 1020 is tilted by the amount, which corresponds to a support clearance C defined between the second rotator 1020 and the first rotator 1010, so that the opposed axial end parts of the second rotator 1020 contact the first rotator 1010.
With the above construction, there are two possible contact states of the second rotator 1020 relative to the first rotator 1010. In the first contact state, as shown in FIG. 8B, the non-protruding portion 1210a of the stopper portion 1200 contacts the first rotator 1010. In the second contact state, as shown in FIG. 8C, the stopper portion 1200 at the large diameter portion 1210 contacts the first rotator 1010. Therefore, the amount of tilt of the rotational axis O of the second rotator 1020 changes from time to time, so that frictional wearing and/or noises may be generated between the gear portion of the second rotator 1020 and the planetary gear.